Bacteria problem? Should I super-shock, drain & refill...

[uberschweiz]

We're pretty new to hot tubs and moved into a place with a nice Cal Spas hot tub. The previous owners set it up for us, fresh water, shock and bromine tabs in the floater. It's been set at 100°F constantly for the last 2 weeks and haven't really bothered to check the levels since they said it would be fine for at 2-3 weeks before checking it.

Longer story short, our girls and their friend came out with a rash we thought was chicken pox only for their pediatrician to say he thought it was a bacterial infection from the hot tub.

So....... how to proceed from there.

I had one person recommend the following procedure:
1) put in about 4 cups of bleach
2) drain hot tub completely
3) scrub inside with some more bleach water, then rinse
4) refill
5) shock & stabilize according to methods seen here on TFP for bromine hot tubs

I'm curious if this will be enough?

Would any of you recommend another method of getting rid of any yuck in there?
Is draining it really necessary, or will a proper strong shock get rid of any organics in the water?

Thanks,
Ben

 

[chem geek]

Re: Bacteria problem? Should I super-shock, drain & refill..

Welcome to TFP!

Bromine tabs in a floating feeder usually don't last much longer than a week or so if there is no bather load, but if the spa is used the bromine level can get too low. Does this spa have an ozonator? If it does, then an initial bromide bank may not have been properly established.

As for decontamination, that requires a superchlorination or use of Spa System Flush or both, but either way you'll drain/refill after doing so. Though you could just do a shock to a higher chlorine/bromine level, that may not be enough and personally I wouldn't take the chance given the infections that occurred. When the sanitizer level gets to near-zero, biofilms can form and those are very resistant to normal or even shock chlorine/bromine levels (especially in spas), hence the more extreme methods for removal.

4 cups of 6% bleach in 350 gallons is 44 ppm FC. That is not bad, but the full decontamination procedure described in this post uses 100 ppm chlorine. Since you don't know the history of this tub, the most extreme approach would first use the Spa System Flush, then drain/refill, then do the decontamination with 100 ppm chlorine, then drain/refill. This may be overkill, but it will most certainly get rid of any biofilms and kill any lingering bacteria.

 

[uberschweiz]

Re: Bacteria problem? Should I super-shock, drain & refill..

Update:

Put 4 cups of Clorox unscented bleach in tonight. Ran the jets for a couple cycles with the lid closed.

Next step?

1) Drain and redo water from scratch....

OR

2) Re-establish bromine levels and proper pH?

 

[chem geek]

Re: Bacteria problem? Should I super-shock, drain & refill..

You'll want to drain and refill the water because you want to remove anything that was in the tub. The chlorinated disinfection by-products or any chemicals not fully oxidized should be removed and that is done with a drain/refill. After your refill, you would then re-establish a bromide bank and use your bromine floater. Just remember that bather load will probably require additional oxidizer (chlorine or MPS) to be added to activate more bromine unless you have a very powerful ozonator.

Note that once you have decontaminated your spa, if you properly maintain it you should not need to go through this again ever.